<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>菜鸟教程(runoob.com)</title>
</head>

<body>

    <p>点击下面的按钮来显示今天是周几：</p>
    <button onclick="myFunction()">点击这里</button>
    <p id="demo"></p>
    <script>
        function myFunction() {
            var x;
            var d = new Date().getDay();
            switch (d) {
                case 0: x = "今天是星期日";
                    break;
                case 1: x = "今天是星期一";
                    break;
                case 2: x = "今天是星期二";
                    break;
                case 3: x = "今天是星期三";
                    break;
                case 4: x = "今天是星期四";
                    break;
                case 5: x = "今天是星期五";
                    break;
                case 6: x = "今天是星期六";
                    break;
            }
            document.getElementById("demo").innerHTML = x;
        }
    </script>

</body>

</html>